Addressing Mechanism
The local network address used in IP-Ethernet is called MAC address because it historically was part of the MAC layer in early Ethernet implementations. The MAC layer's addressing mechanism is called physical address or MAC address. A MAC address is a unique serial number. Once a MAC address has been assigned to a particular network interface (typically at time of manufacture), that device should be uniquely identifiable amongst all other network devices in the world. This guarantees that each device in a network will have a different MAC address (analogous to a street address). This makes it possible for data packets to be delivered to a destination within a subnetwork, i.e. hosts interconnected by some combination of repeaters, hubs, bridges and switches, but not by IP routers. Thus, when an IP packet reaches its destination (sub)network, the destination IP address (a layer 3 or network layer concept) is resolved with the Address Resolution Protocol for IPv4, or by Neighbor Discovery Protocol (IPv6) into the MAC address (a layer 2 concept) of the destination host.
An example of a physical network is an Ethernet network, perhaps extended by wireless local area network (WLAN) access points and WLAN network adapters, since these share the same 48-bit MAC address hierarchy as Ethernet.
A MAC layer is not required in full-duplex point-to-point communication, but address fields are included in some point-to-point protocols for compatibility reasons.
Read more about this topic: Media Access Control
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